Coffee and tea pots have been used for centuries to brew coffee or tea. The common method has been pouring hot water over the coffee grinds or tea leafs, and allowing the water to infuse and extract the soluble solids from the brew product. A later improvement provided a straining means located near the opening's neck permitting the brewing to take place without having to sift the brew leftover from the beverage. This improvement was advantageous but required removing the straining device prior to pouring. This drawback has been overcome with a stopper/cap that comprises both an opening for pouring the beverage and an opening for the strainer/filter.
As people get busier, they do not have time for brewing a perfect cup of coffee or tea notwithstanding a brewing pot that conveniently separates the brew leftover and the brew. Furthermore, they also want to keep their beverages warmer longer so they can get the best tastes. These desires have been met with a vacuum mug, or thermal mug, that insulates the beverage inside from the temperature outside, and has become a modern convenience that busy coffee or tea drinkers cannot function without. A vacuum mug with a stopper cap that comprises both a strainer or filter, and an opening for sipping has allowed a coffee or tea drinker to brew her coffee or tea on the go as if the user takes a brewing pot with her. The vacuum mug keeps the hot water hot, so the coffee or tea inside the strainer filter has time to brew while the user travels to the workplace.
The more convenient and functionally better vacuum mugs get, the more often people use them. Thus, naturally, they want their mugs to be ever larger or taller, to contain larger quantity of their drinks, so that they do not have to refill their mugs so often. Since the mugs are getting larger, they post a problem of inconsistent quality of the brewed beverage. For example, over extraction, due to brewing ground coffee in consistently hot water for a long period, results in intensely bitter coffee, while under extracted coffee, due to cooler water and/or shorter brewing period, is usually sour and lacking in complexity. With a larger or taller mug, this problem will be exacerbated where a small strainer/filter is attached under the cap near the top, and half empty beverage is at the bottom of the tall mug, and the brewing stops when the user drinks too fast. This scenario is actually common when people are busier.
However, a single deep filter will not be a good solution either because the entire amount of the brew product stay submerged at the bottom of the filter, and the longer the coffee or tea is submerged in the water, the longer the brewing time and, thus, the more likely an over extraction, and bitter beverages. Thus, it is desirable that the user has some finer control of the brewing.
Furthermore, for drinkers who like to add flavor ingredients to their beverages, they do not have a way to add the flavor ingredients except putting the ingredients directly into the coffee or tea leaves before brewing. In some instances, mixing flavor ingredients and brew product Is not desirable. In other instances, submerging the flavor ingredients in the beverage for a long period is not desirable. Perhaps, in these instances the drinker only wants a mild flavor.